Automatic door opening mechanism



p 1934. A. s. FITZ GERALD 1,972,682

AUTOMATIC DOOR OPENING MECHANISM Filed June 12, 1930 Alan S. FibzGewaici b z/ m/ His Atoowne Patented Sept. 4, 1934 PATENT OFFICE AUTOMATIC DOOR OPENING MECHANISM Alan S. Fitz Gerald, Wynnewood, Pa., assignor to General Electric Company, a corporation of New York Application June 12, 1930, Serial No. 460,783

1 Claim. (Cl. 250-415) The present invention relates to light sensitive systems and more particularly to apparatus such as door-opening mechanism whose component parts operate in mechanical sequence and whose operation is initiated or controlled by the response of light sensitive devices.

In places where rooms adjoin and communicate through swinging doors, also in the case of garage doors and air-lock doors in mine haulages, it is often desirable to have the door open automatically when a person or object approaches and to close immediately after the person or object has passed through the doorway. An arrangement of this sort is particularly useful in the case of doors which connect a dining room to the kitchen of a restaurant or hotel and which are continually being opened by waiters or others whose hands may not be free to push the door.

An object of the present invention is to provide an improved arrangement for opening and closing a door or equivalent member by means of a light-sensitive device and an impinging light beam. Other objects and features will be apparent as the specification is perused in connection with the accompanying drawing, in which Fig. 1 shows in diagram the improved door opening mechanism with the light control devices in place, while Fig. 2 illustrates a circuit which may be satisfactorily employed in the arrangement shown in Fig. 1.

Referring to Fig. 1, numeral 1 designates a wall, which may be the exterior wall of a building such as a garage, or which may be common to two adjoining rooms, or compartments which communicate through a door 2. The latter is connected to any well known and suitable type of electrically operated door-opening device 3 through a lever system 4 in the usual manner.

The device 3 may take on various forms known to the art but I prefer to employ for this mechanism an electro-hydraulic operator, for example, such as disclosed in patent application, Serial No. 415,341, entitled Hydraulic operator, filed December 19, 1929, in the name of Walter O. Lum.

An operator of this kind consists essentially in a motor of any suitable type, which drives an impeller for forcing liquid between a piston anda cylinder head. The other end of the piston terminates in a bracket which is rotatably secured to a bell crank lever 5. When the motor is energized, the liquid under pressure moves the piston upwardly and rotates the lever 5 to exert a longitudinal pull on the rod 4 which opens the door. When the motor is deenergized, the liquid flows through passageways from one side of the piston exerts no force on the piston whereby the latter is forced downwardly by a compression spring (not shown) and by reason of its own weight, so that the rod is pushed longitudinally to close the door.

It will be understood that while I prefer for reasons stated presently the type of hydraulic operator described, my invention is not limited thereto, but contemplates the use of any form of door opening mechanism which is further operable by the application of electrical energy either directly or indirectly to a moving member. It is evident that well-known lever systems actuated by a motor through worm and gear, also mechanism employing compressed air, powerful solenoids and electromagnets, may be used for this purpose. Hydraulic or other forms of fluid operator such as those employing compressed air and all of which are actuated by an electric motor offer advantage in connection with doors or other members movable back and forth, between two positions. Operators of this sort may readily be designed to give cushioning efiects on the up and down stroke of the piston which are particularly well suited to the opening and closing movements of a door or to the reciprocations of any other rapidly movable member. These cushioning effects tend not only to render the operation of the moving member noiseless but also to relieve the impact at the supports, framework or hinges in the case of the door, with resultant increase of operating life. Moreover, most forms offluid operated devices use oil for the propelling medium which serves also continually to lubricate the moving parts.

As will be explained hereinafter, the motor in the operator is energized from a suitable source of alternating current through a three blade switch, in the case of a three-phase induction motor, which switch is closed or opened, depending upon the light condition of light-sensitive devices 6, 6. The latter may take the form of selenium cells, but I prefer photo-electric tubes of any efiicient and well constructed type. These tubes are typically shown as being secured to a standard 7, one on each side of the door and positioned in such a manner as to be activated by light sources 8, 8 when the light beam is uninterrupted. It is convenient to mount the light sources, which may constitute ordinary incandescent lamps energized from the common source of current supply and provided with a suitable reflector, also on a standard 9 at the same height as the photo-electric tubes so as to project a horizontal beam 10 toward the latter.

The distance between the standards of each unit and their position with respect to the door should be such that a person desiring to have the door opened from either side would merely have to walk between one pair of standards, or in any other manner to intercept the light beam and to cause the actuation of the door opening device, as will be explained hereinafter. However, it will be understood that the arrangement and relative positions of the photo-electric tube and light source depend upon the location of the door with respect to near-by walls, i. e. the lay-out of the room or compartment, and it may be possible to eliminate the standards entirely. It may even be convenient and in some cases preferable to mount the lamp in the ceiling above the door and .the photo-electric tube on a nearby wall, or in the floor, so that a light directed diagonally or vertically downwardly would traverse an area in front of the door. Some of the arrangements oifer advantage over others with respect to the concealment of the current supply wires and as offering little or no mechanical obstruction in the vicinity of the door.

Referring to the circuit diagram of Fig. 2, the light-sensitive tubes 6 are connected across the input circuit of two independently operating three-electrode amplifiers 11, 11, which are energized by alternating current through a transformer 12. There is a grid leak resistance 13 of about two megohms connected between the anode of each photo-electric tube and the more positive side of the respective filaments during the positive portion of the voltage cycle. The function of this resistance is to cause the grids of the amplifiers to go positive when the light beam impinging on either photo electric tube is interrupted. The output circuits of the amplifier contain, in common, a sensitive relay 14 which when energized, attracts an armature 15 toward a stationary contact 16.

It will be apparent that only one photo-electric tube is operated at a given moment since these tubes are mounted on opposite sides of the door and serve to cause the latter to open in the same direction when their respective light-activating beams are interrupted by a person desiring to enter. However, if desired, one-way doors, opening in opposite directions in response to individual photo-electric tube and hydraulic operator units, may be provided. As exemplified, the current through relay 14 is under the individual but nonexclusive control of each light-sensitive device and its associated amplifier. It will be further noted that the units comprising the photo-electric tube and amplifier are effectively connected in parallel with respect to the relay.

The armature 15 and contact 16 form part of the input circuit of a three-electrode device 17, the contact being connected through a resistance 18 to the grid and the armature being connected through a fairly high adjustable resistance 19 to the mid-point of a filament transformer winding 20. The resistance 19 is energized by means of a well known full wave bridge arrangement 21 of rectifiers, preferably of the copper-oxide type, the latter being connected directly across the alternating current mains 22. Connected between the resistance 19 and the grid of the amplifier, also effectively in shunt to the armature-contact device 15, 16, there is a time delay circuit consisting of a condenser 23 which may have a value of about 5 to 10 microfarads and a resistance 24 Langmuir Patent No. 1,289,823. A device of this sort'is characterized by an output of the order of many amperes which is controllable by a grid voltage of a few microwatts. When an amplifier of this kind is energized by alternating current, the grid merely controls the starting of the are by "trigger action, but thereafter may lose control during the remainder of the positive half cycle.

The input circuit of the amplifier 28, also the output circuit of the previous amplifier 17 are energized from the secondary coil of a transformer 29 whose primary is connected to the supply mains 22. The output circuit of the device 28 is connected directly across the supply circuit by conductors 30 which include as part of the circuit a relay 31 preferably of the solenoid type and having a movable core 32. This core has secured thereto along its length a plurality of contact members 33 which, when the solenoid is energized, bridge the gap between respective pairs of stationary contacts 34, thereby completing the circuit from a source of current supply (not shown) to the door opening motor. This circuit may constitute a three-phase, 60 cycle, 220 volt supply in order to energize a motor of the type usually provided in the well known type of electro-hydraulic operator referred to hereinbefore.

The operation of the door opening arrangement will be clear from an inspection of the circuit and the following explanation. When the door is closed and the light beams are uninterrupted, the light falling on each photo-electric tube causes the grid of each amplifier 11 to remain at the negative bias established by the negative current flowing through the photoelectric tubes during one-half cycle of the energizing current. The plate current under these conditions, is at a low value, practically zero, and the relay 14 remains deenergized with the contacts 15, 16 open, thereby maintaining the condenser 23 in a discharged condition clue to the shunt relation of resistance 24. The fact that the load across the condenser is substantially zero keeps the potential of the grid in the amplifier 17 relatively low and allows the plate current in the amplifier to assume a large value, for

example, of the order of 4 or 5 milliamperes. This current fiows through the plate load resistance 25, 26 causing a high voltage drop therein and this potential difference is applied as a high negative bias to the grid of the arc discharge device 28, preventing a discharge in the latter.

It will thus be seen when the light beams are uninterrupted, substantially no current flows through the last amplifier, and the electromagnet 31 remains deenergized, whereby the circuit to the motor in the door-opening mechanism is open. In order to adjust the system, it is necessary to move the slider at the end of resistance 26 to such a position on the secondary of trans- 50 light beam the photo-electric tube conduction is stopped and the grid of amplifier 11 assumes a potential corresponding to the more positive end of the cathode of the amplifier, due to resistance 13, which causes the amplifier to draw current in order to energize relay 14, The armature 15 now contacts with the member 16, so that condenser 23 to which it is connected, is charged substantially to the full potential of the doublewave rectifier 21 and in such a direction that the plate current in amplifier 17 is reduced substantially to zero. The voltage across resistance 25 becomes zero and allows the grid of the last amplifier to become so positive as to approach cathode potential.

An. arc. discharge is therefore produced in the tube 28 during one or more positive half-cycles depending on the length of time the device remains triggered and the large output current picks up the contactor 2'7 to energize the door operating mechanism. The door remains open until the time delay condenser 23 is discharged by its shunt resistance and the original condition restored. The time during which the door will remain open may be varied by adjusting the voltage which charges the condenser.

It will be understood that the operation of the system, as shown, is predicated practically entirely on the positive half-cycle of the voltage obtained from the alternating current supplycircuits. The negative half wave of the supply voltage is unused except in the copper-oxide double wave rectifier.

While I have explained my invention in connection with an alternating current source of supply, it is evident that direct current may be employed when suitable and obvious changes are made in the system. One such change would be to substitute an ordinary form of power tube for the arc discharge device 28 and as another alternative, to provide the tube 28 with a well known form of interrupting device in its plate circuit, thereby to cut off the arc discharge at any predetermined time after being triggered. Many other modifications will readily suggest themselves to those skilled in the art, such as the elimination of one or more amplifying stages in the event that relay 31 requires only a small current for energization purposes.

It is also within the contemplation of my invention to have the door opened under conditions of the light-sensitive tubes, difierent or opposite to that described, as for example, when the tubes are activated, rather than inactivated due to the interruption of the light. It is evident that when obvious changes in the system are made, paramplifier, a person approaching the door may cause a light beam to impinge on the light-sensitive member as by reflection which would operate the door opening mechanism. In this case, the photo-electric tube may be mounted on the same side of the door as the light source, so that a person or object in moving toward the door would cause a portion of the light beam, which normally would be radiated into space, .to be refiected and re-directed toward the tube.

It may also be desirable to have the door operate more quickly when approached by a person or object in the direction against which the door opens than when the door opens in the same direction and for this purpose, individual relays having different time constants may be provided for the respective photo-electric tube units instead of the single relay 14, common to both units. a

From the foregoing, it will be evident that I have described a novel arrangement for opening and closing doors which responds to interceptions of a light beam normally directed or reflected onto a light-sensitive device. Such interception of the light beam is produced in a positive manner by the object or person entering the doorway and is independent of the physical character or size of such object or person. Consequently, the impulse for initiating the door opening function is always positive and of a constant predetermined amount. The only permanent installation required is that of the operator and associated linkage, also of the light source and light-sensitive device, and such installation necessitates no moving contacts or other elements calling for constant attention. The permanent installation is of a simple character in that it utilizes the minimum number of parts and requires the smallest amount of change in the existing structure about the door. The electrical system associated with the permanent installation and which includes the members as may need to be adjusted, conveniently may be installed in any accessible place where such adjustments and the necessary replacements can be effected without interfering with the permanent portion of the installation.

What I claim as new and desire to secure by Letters Patent of the United States, is:

In combination, a member adapted to move between two positions, electro-hydraulic means for moving said member from one position to the other position and return, means for energizing said electro-hydraulic means, a light-sensitive device for controlling said energizing means, and means operating independently of said lightsensitive device for maintaining the electro-hydraulic means energized for a predetermined length of time before said member is returned to its original position.

ALAN S. FITZ GERALD.

CERTIFICATE or CORREETION.

Patent No. 1,972,682. September 4, 1934.

ALAN s. FlTZ GERALD.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 66, strike out the word "further" and insert the same before "evident" in line 69; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of October, A. D. 1934.

Leslie Frazer (Seal) 6 Acting Commissioner of Patents. 

